Device for producing castings that comprises a wall can be guided into the casting mold

ABSTRACT

The invention relates to a device for producing castings from flowable or strewable starting material. Said device comprises an injection unit, out of which the at least partially liquefied material can be injected into a casting mold. The injection unit has an inlet opening for supplying the material, and the injection unit has a chamber with two moveable walls. These walls can either be moved together in one direction or in opposite directions in such a manner that the volume of the interior of the chamber can be altered as desired and/or the interior of the chamber can he displaced, whereby one or both walls form a portion of the wall delimiting the mold cavity. The invention provides that both walls each form a portion of the wall delimiting the mold cavity, whereby one of the walls can be guided into the casting mold.

[0001] The invention relates to a device according to the preamble ofclaim 1.

[0002] European Patent 1 046 444 A1 discloses a device of this typeaccording to the species. Three pistons are used to create avariable-volume chamber for the injection material. In it, two pistonsare axially movable within a tubular cavity, and a third piston can bemoved perpendicularly to the longitudinal axis of the chamber betweenthe two above-mentioned pistons so as to convey the material into themold cavity. The requirement here is that there be a precise sealbetween the three pistons relative to one another and to the chamber.Because of the space requirement and the demands on the seal, the deviceaccording to the species is very expensive to produce.

[0003] German Patent 199 14 830 A1 describes a device in which two wallsdesigned as a valve and a piston are axially movable within the tubularcavity. They adjoin a runner through which the injection material entersthe actual mold cavity.

[0004] German Patent 43 10 755 A1 describes a device in which two walls,one designed as a nondriven movable clamping disk and the other as adriven piston, are axially movable within a tubular cavity. They adjoina runner through which the injection material enters the actual moldcavity.

[0005] Replaceable mold inserts which may form sections of the wall ofthe mold cavity are known from Ernst Brunnhuber, “ModerneDruckgussfertigung” [Modern Die-Casting], Fachverlag Schiele und SchönGmbH, Berlin, 1971, pages 137 and 139.

[0006] The goal of the present invention is to improve a deviceaccording to the species so that it is as efficient as possible, hascompact dimensions, and can be operated as inexpensively as possible.

[0007] This goal of the invention is achieved by a device having thecharacteristic features of claim 1.

[0008] In other words, the invention proposes an approach in which themovable chamber walls are located not exclusively outside the mold butare disposed to allow displacement of the chamber contents into themold. This approach results in a savings in material since the sprue canbe avoided or considerably reduced. As a result, a reduction can be madein the quantity of material in circulation which must be re-cooled andre-melted for each cycle, with the possible ensuing melting loss inexpensive alloy elements, this melting loss having to be continuallyreplaced.

[0009] Since the sprue/runner can be reduced or completely eliminated,the amount of heated material, and thus the heat load on the injectionunit and the mold itself, are also reduced, thereby allowing for shortercool-down phases and consequently for a higher number of pieces producedper unit time.

[0010] Since the material enters the mold directly from the chamberwithout any intermediate injection channel, larger flow cross-sectionscan be used and, as a result, possible deviations in material flow canbe avoided. The material therefore does not need to be heated to as higha temperature as it otherwise would to permit the optimal flow-throughcapability into the mold for comparatively smaller inlet ports or topermit the proper flow over long distances. The result is that a lowertemperature level can be set for the molten metal—with the result thatthis measure allows the heat load on the device to be reduced, asalready mentioned, shortens cool-down times, and enhances the efficiencyof the device.

[0011] The fact that deviations in material flow can be avoided allowsthe load on the device to be reduced since such deviations may result inpremature wear and actual erosion. In addition, this fact may allow fora reduction in required impelling power since the conveying resistanceof the material can be reduced.

[0012] The fact that the injection unit extends into the mold and is notlocated exclusively outside the mold means that the device can beproduced with compact dimensions. This feature is enabled specificallyby the fact that one of the two walls does not merely extend up to theedge of the mold but may be moved into the mold.

[0013] One of the two movable walls of the injection unit chamber may beadvantageously designed as the section of the wall of the mold cavitywhich is designed to be movable for the purpose of opening the mold.This approach avoids complex multi-axial movements and ensures that,when the mold is opened, this injection unit wall, which is movable intothe casting mold, is moved together with the section of the mold to heopened—thereby allowing the access to the casting when the mold isopened to remain unchanged and allowing optimal access to the castingfor its removal.

[0014] The following discussion utilizes an embodiment to explain theinvention in greater detail.

[0015]FIGS. 1 through 6 show a device for producing castings at variousphases of the casting process.

[0016] Reference 1 in FIG. 1 designates a device for producing castingsin a pressure die-casting process.

[0017] Device 1 has a two-part mold 2 which in FIG. 1 is seen in itsclosed configuration. Device 1 additionally has an injection unit 3which serves to inject the fusible material into the mold 2. FIG. 1shows injection unit 3 in an initial phase of its filling process:

[0018] A conveying unit 4 conveys the molten or at least partiallymolten material into a chamber 5 of injection unit 3. The chamber wallsare formed by a round tube 6, an injection piston 7, and a sealingpiston 8.

[0019] In FIG. 1, the volume of chamber 5 is comparatively small. Thechamber volume can be kept to an extreme minimum by moving the twopistons 7 and 8 very close together. There is assurance at all timesthat even oxidation-prone material can be readily processed since anycontact with ambient air is essentially precluded. The material isconveyed by conveying unit 4 into chamber 5, while sealing piston 8 isincreasingly moved away from injection piston 7 to adjust for thequantity of admitted material, as FIG. 2 shows.

[0020]FIG. 2 shows injection unit 3 in an end phase of filling wheninjection unit 3 is essentially filled with the casting material. Thevolume of chamber 5 has increased accordingly, and injection piston 7continues to be situated at a position in which the access for conveyingunit 4 into chamber 5 is open.

[0021] Once the desired quantity of material has been admitted tochamber 5, the two pistons 7 and 8 move together. As is evident in FIG.3, the result is that chamber 5 is now closed relative to conveying unit4.

[0022] Sealing piston 8 is moved out of tube 6 and into mold 2. Thisaction opens tube 6 and thus, chamber 5. A further movement of injectionpiston 7 causes the material to be injected from chamber 5 into mold 2.

[0023]FIG. 4 shows the end position of injection piston 7. Sealingpiston 8 is located inside mold 2 at a position in which it forms partof the wall of mold 2, which part limits the mold cavity 9 which in turndetermines the subsequent contour of the casting. In the embodimentshown, this is a casting, for example, a rotationally symmetricalcomponent such as a wheel, a cover, or the like, in the shaping of whichsealing piston 8 directly participates, and which may be accordinglydesigned so as to determine the desired surface shape of the casting. Inthis case, the sprue point into the casting can be displaced such thatadvantageously there is no “sprue” in the conventional sense, i.e., apart which must be removed from the casting and can be used only asrecycled material.

[0024] Alternatively, the approach may be to have one or more individualend products arranged radially around the region of the two pistons 7and 8 such that the casting produced comprises this number of productsplus a sprue which extends from the region between pistons 7 and 8 up tothese products. The sprue is thus minimal and has no componentsextending out of the actual mold 2. In this case, injection piston 7 canextend further than shown in FIG. 3 to keep the material thickness ofthe sprue as small as possible.

[0025] In FIG. 5, it is evident that mold 2 is open. For this purpose,mold 2 consists of a fixed mold section 10 and another movable moldsection 11. Sealing piston 8 is supported within the movable moldsection 11 and is movable together with or separately from movable moldsection 11 such that, after mold 2 is opened, the casting can be removedeasily and with the same accessibility as with a conventional injectionunit in which all the components are located outside mold 2.

[0026] After removal of the casting, movable mold section 11 may againbe moved toward fixed section 10 of the mold. This motion results alsoin sealing piston 8 being moved toward injection piston 7 which hasremained in its end position. FIG. 6 shows in purely schematic form thatscaling piston 8 has preferably been moved up to injection piston 7 inorder to create a minimum volume in chamber 5 before mold 2 iscompletely closed. This allows for easy venting of the surroundingatmosphere so that chamber 5 is set for a minimum chamber volume. Forsafety reasons only, meaning the avoidance of mechanical damage topistons 7 and 8, the design of the piston control shown provides thatpistons 7 and 8 do not directly contact each other.

[0027] Starting with the status shown in FIG. 6, mold 2 is closed, i.e.,the movable section 11 is moved completely against fixed mold section 10after which the backplates of mold 2 are locked so that it is ready toreceive the injection pressures.

[0028] One advantage of the device according to the invention is thatsealing piston 8 is allowed to rest against movable mold section 11during the injection procedure—with the result that, advantageously, noexpensive and design-specific provision has to be made in terms of aseparate support for sealing piston 8 since the injection pressuresacting on sealing piston 8 are accommodated by mold 2 or its backplates.

[0029] Subsequent to the situation in FIG. 6 and after mold 2 has beenclosed, chamber 5 is displaced by a movement of the same direction andspeed effected by pistons 7 and 8 until chamber 5 is situated in frontof the opening of conveying unit 4 so that a new operating cycle cantake place.

1. Device for producing castings out of fusible or dispersible basematerial, including an injection unit from which the at least partiallyliquefied material can be injected into a mold, wherein the injectionunit has an inlet port for feeding the material, and wherein theinjection unit has a chamber with two movable walls which may as desiredbe moved either together in the same direction or in opposite directionsso that the cavity of the chamber may be varied by volume as desiredand/or be displaceable, one of the two walls forming a section of thewall delimiting the mold cavity (9), characterized in that the two wallseach form a part of the walls delimiting the mold cavity (9), one of thetwo walls being movable into the mold (2).
 2. Device according to claim1, characterized in that the wall which is movable into the mold (2) isdesigned as a piston (8) which is supported within a tubular chamberwall so as to be longitudinally movable or is supported so as to bemovable toward chamber (5) to perform a sealing function, and that thiswall is movable together with a movable mold section (11) of mold (2).3. Device according to claim 1, characterized in that the wall which ismovable into mold (2) is designed to partially determine the surfaceshape of the casting.